X-ray tube control apparatus



Dec. 29, 1964 J. FRANSEN 3,163,757

X-RAY TUBE CONTROL APPARATUS Filed My s, 1961 is 8 6 {I {f r/ 1 2 Voltage stablllzer r 56 g 2 5 2 'Jo r 1. D 31 .H. 58 IL comparatr r 53 5g? I signal indicator 60 srstem F IG.1

INVENTOR JA COBUS FRA NSEN 5:80 ,6 AG; T

United States Patent 6 This invention relates to radiographic apparatus and 'more particularly to improved load adjustment means thereof.

A beam of X-rays or v-rays, propagated through any heterogeneous object, is differentially absorbed, depending upon the varying thickness, density, and chemical composition of the object. Thus, the nature and, in addition, the activity of a specimen to beradiographically examined must be considered in determining the load adjustments to be made for the examining radiographic apparaths. To this end, in known type of radiography apparatus, as for example, those of the X-ray variety, separate independently actuated adjusting means are provided for adjusting, respectively, the high voltage supplied to the apparatus X-ray tube, the filament current sup plied thereto, and the time of exposure. For each particular type of object to be radiographically examined, an optimum range of voltages con rolling penetrationand of time of exposure are available. in this range, there is an exposure value equal to the product of the filament current and duration of the load period, the latter being proportional to the exposure time. Charts, or tables, are available in which the exposure values are plotted graphically against, or tabulated for, difierent thickness of specimens of a particular composition for these different voltages. The adjustment of the high voltage value is generally determined by the nature of the object in which the factors of its composition and thickness are considered in relation to beam pentration. The adjustment of the load period generally involves the consideration, inter alia, of the activity, i.e. relative movement, of the specimen in relation to the optimum definition obtainable for the radiograph. Thus, with a knowledge and/or observation of the thickness, and composition of a particular object, a plurality of voltages within the aforesaid range are available from which to choose the tube voltage adjustment, and the determination of which of these voltages is the proper voltage to choose for the particular specimen is often difiicult for the operator to resolve. Once a single voltage has been selected, then consolation of the graph or table will yield the required associated exposure value.

For each voltage I v 3,153,757 Patented Dec. 29., 1964 "ice It has been found to be more efficacious in some of the prior art apparatus to adjust the-tube voltage and the product of. the tube current and load period instead of adjusting the tube voltage and the load period with the quality of a radiograph provided by such apparatus beingmainly determined then by the tube voltage and this product, referred to, hereinafter, asthe milliamperesecond product (ma.-sec.-product). Therefore, these known X-ray apparatus usually comprise an indicating device for the ma.-sec.-product. Thus, the control of an apparatus having relatively independent adjusting means becomes more complicated since not only the maximum permissible current but also the ma.-sec.-product varies with the adjustment of time. In a known device comprising a current adjusting means coupled with a voltage adjusting means and time adjustment means, the time is adjusted to the shortest possible duration for each selected value of the ma.-sec.-product,' which, however, does not necessarily always yield the most efiicient combinations.

Moreover, various safety members to prevent overloading of the X-ray tube havebeen suggested in the prior art, which members produce a monitoring signal in the event of an erroneously chosen adjustment and/or prevent the X-ray apparatus from becoming operative. Howevere, the aforesaid disadvantages are only partly obviated, since the efilcient choice of the load magnitudes is not facilitated. 7

An object of this invention is-to provide radiographic apparatus which provides for the selection of various load 7 1 adjustments which will yield the most efiioient combina- However, s nce this exposure value is the product of two variables and is equal to a constant, for a given volt age value, a plurality of combinations of time and current values are likewise available and further compound and complicate the operators sel ction of adjust ments. Furthermore, the tabulated or plotted exposure values are generally based on the maximum permissible filament current which may not always be the most efi'icient value for a particular combination of the variable factors involved. Thus, if the time of exposure is next selected after selection of the operating voltage, a maximum filament current adjustment is derived based on an exposure value obtained from the graph or table. Radiographic apparatus of the prior art are known which provide automatic compensation means for adjusting the filament current in response to the preselected adjustments of the tube voltage and preselected time of exposure. However, these automatic compensation means of the prior-art apparatus are equally unsatisfactory since the filament current is automatically adjusted to limit the current to the maximum permissible value which, as aforesaid, may not always be the most eificient setting.

tion for each particular specimen to be examined.

Accordingly, this invention features a coupling means having a first position which couples the current adjusting means and time adjusting means of an associated radio,-

graphic apparatus in relative responsive relationship with each other to maintain the product of the'magnitude of the signal current and time period constant whenever either of these adjusting means is adjusted and a second position which couples these adjusting means in an independent relationship with each other whenever either of these two adjusting means is actuated.

Another feature of this invention is the provision of a safety means to prevent overloading of the apparatus due to an incorrectcombination of adjustments of any of e the adjusting means provided in the apparatus.

to the following description taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a schematic diagram partially in blockform of the radiographic apparatus of this invention; and

FIG. 2 is a partial structural diagram of an embodiment of the radiographic apparatus of this invention.

Broadly,.the radiographic apparatus of this invention comprises a device, generally denoted by the reference letter A, FIGJL- adapted to produce a beam of rays for radiographic inspection of an object (not shown). Associated with the; device'A are a suitable" source of signal potential, a suitable source of signal current, and a timing means, generally denoted by the reference letters B, C and D, respectively, FIG. 1. Various adjusting means for the sources B and C, and timing means Dare also provided and are indicated generally in FIG. 1 by the reference letters E, F, .G, respectively. A coupling means H is provided which has two positions, one of which couples the signal current and timing adjusting-means in relative responsive relationship with each other to. -maintain the product of the magnitude of the signal'current and time period constant whenever either. of these two adjusting means is adjusted and 'thesecond position of whicn couples these two adjusting means in independ cut relationship with each other Whenever either one of them is adjusted, as will be explained in greater detail hereinafter. A safety means, illustrated in FIG. 1 generally by the reference letter J, is also provided which prevents overloading of theapparatus of FIG. 1 in the event any of the three adjustments are invalidly combined as will also be explained in greater detail hereina ter.

Referring to FIG. 1 in greater detail, an electron discharge device for generating a beam of rays for, radiographic inspection of an object (not shown) is illustrated, by'way' of example only, as a tube adapted for generating X-rays. The device has a collector and emitter electrode adapted to produce the beam of rays from electrons emitted from the emitter electrode, in a manner well known to those skilled in the art and are illustrated as the anode and cathode electrodes 12, 13, respectively, of tube 10. To provide a source of high voltage for tube 10, thesecondary winding 11 of a high voltage transformer 8 is shunted across the anode electrode 12 and cathode electrode 13 of tube 10. The primary winding. 7 of transformer 8'is coupled, via various adjusting means and/or switching means, to the conductors 1, 2, which represent voltage mains connected to a suitable source,

not shown, of signal potential, aswill be described in greater detail hereinafter.

The .filament current for tube 10 is provided by filament-current transformer 15 whose secondary winding 14 is coupled to the cathode electrode 13 in a manner wellflknown'to those skilled in the art. The primary winding 16 of transformer 15 is coupled, via current adjusting: means. F, illustrated, for example, as an adjustable rheo stat17, and via voltage stabilizer 18 and switch. 17, to the. conductors, 1, 2. Voltage stabilizer 18, illustrated, schematically; in block form, is provided to compensate for fluctuations. in the. signal voltage appearing in the conductors 1, 2, when switch 17 is placed in the closed position.

To control the load period of the tube 19, i.e. the time of exposure, timing means D is associated with the tube ltland has adjusting means G to adjust the length of time that, the high voltage of transformer 8 is applied to tube10. For example, as illustrated in FIGURE 1, the, timing means comprises an electrically operated adjustable timing switch 19, illustrated in block form, which is coupled to the conductors 1, 2 via switch 19'. The adjusting means. 20,-illustratedas an adjusting arm of switch 19 is positioned to provide some predetermined transformer 8, and apply the high voltage to the tube 10. Upon expiration of the adjusted predetermined period, coil 21 is de-energized and switching'element 22. opens. contacts 22 removing the high voltage supplied .by transformer 8 from tube 10. 1 j e 1 The voltage adjusting means associated with the tube 10 comprises a control transformer illustrated, by way of example only, as an autotransformer.3 having an ad-' justableinput 5 coupled to the conductors 1, 2 via switch 3 and adjustable matching resistor 4. A meter .6 is. shunted acrossthe input to transformer 3 and indicates the magnitude. of the signal there applied; An adjustable output means is provided on transformer 3 and is illustrated, by way of example only, as having several, variously spaced taps connected to the contacts of a stepping. switch 9, the latter having a movable arm 9, the position of which determines, inter alia, the magnitudes ofthe signal applied to the input of the primary-winding 7 of ing of the transformer 3, and similar to the adjustable input means 5, may also be utilized, in lieu of the illustrated tapped output winding of transformer 3 and stepping switch 9, in a manner well known to those skilled in the art.

In order to compensate for certain voltage losses that occur due to changes in the power consumption and filament current caused when adjustments are made in the voltage and/or current adjusting means, voltage regula tion means for tube it) are provided. For example, to compensate for voltage losses caused by adjustment of the voltage adjusting means and voltage losses. caused by the adjustment of the current adjusting means, serially tional to the magnitude of the signal potential applied across the electrodes of tube 10 and, thus, compensates for anyvoltage loss which occurs because of the change in power taken by tube 16) when arm 9 is moved. To compensate for voltage losses which occur because of the displacement of movable arm 27 of rheostat 17 of the current adjusting means, the auxiliary winding 25 is provided with a plurality of output taps which are connected to therespective contacts of a stepping switch 26. The stepping switch 26 has a movable arm 26' which is actuated by the movable arm 27 of rheostat 17 as, for ex ample, by a mechanical connection such as a shaft, illustrated as the dashed line 36,- to which the arms 27 and 26' are commonly ganged. The position of arm 26' with respect to the winding 25 is such that a voltage of sufli-. cient magnitude will be induced in the input circuit to the high Voltage transformer 8 which will compensate for the associated voltage loss caused by the movement of.

arm 27. It is to be understood, however, that the output means of auxiliary winding 25 may be of a continuous type in lieu of the illustrated tapped output winding 25' and stepping switch 26. As mentioned hereinabove, be-. tween time adjusting means G and current adjusting means F, coupling means H is provided which depending on its relative position allows these two means, F and G, to be either in a first position of responsive coupling relationship relative to each other or in a second position of independent coupling relationship witheach other. whenevereither of the means F and G are adjusted. Thus, an operator,-after selecting a suitable operating voltage-for tube 10 by adjustment of the arm 9' and/or input means 5' and with the coupling means 28- in the aforedescribed second position, could individually adjust V the time and current adjusting means via adjusting means 20 and 17, respectively, toyield a.ma.-sec.-product as found from the tables or charts associated with the specimen to be examined. Thereafter, the coupling means 28 most efficient adjustment combination and, at the same time still maintain the selected ma.-sec.-product constant,

transformer 8. It is to be understood, however, that the.

output means of transformer 3 illustrated in FIG; 1 are chosen by way of example only and that adjustable output means of acontinuous type, such as those comprising a movable wiper arm adaptedto sweep the output windi.e., for a given or preselected exposure value. In the alternative, the means 28 may remain in its second posi tion so that each ofeither the time adjusting means or current adjusting means may be individually and independently adjusted for a givenadjustment of the other so as to provide an 'efficient adjustment. combination whichwillyield an exposure value that may or .may notbe equal to the exposure value derived from the chart or: tables. To help facilitate the selection of themagnitudes ofthe various adjusting means, the coupling means H, as well as the individual adjusting means E, F, G,

may be suitably calibrated, in a manner well known to those skilled in the art.

To prevent overloading of tube because of any invalid adjustment of adjusting means E, F, G, a safety member I, as afore-mentioned, is provided and may comprise, for example, a series of inter-related networks such as the reference sources 50, 53 and adjustable resistors 49, 52, 54, 55 whose movable members are in responsive coupling relationship with the respective movements of the adjusting means to provide a reference signal and av signal proportional to the selected adjusted load values. The signals are compared via suitable comparison means 59, illustrated in block form and of a type well known per so, which in turn may actuate a signal indicator system 60, also illustrated in block form, which may automatically prevent operation of tube lil or which may actuate some visible and/ or audible indicator warning device.

Referring to FIGURE 2, the structure of an embodiment of the radiographic apparatus of this invention in which a mechanical coupling means is utilized, is partially illustrated. Accordingly, through the wall 29, which may be thepover of an operators control desk, are disposed three shims s0, s1 and 32, each of which is provided with an adjusting knob 33, 3 and 35, respectively. The tube current of tube 19, PEG. 1 is adjusted by the movement of the knob 33 and the tube voltage by movement of the knob 35. Knob 34 adjusts the load period of tube 10. Ar%ed to the shafts Sll, 31 and 32 are the sliding contacts of movable arms 27, 2 3' and d, respectively, which are associated with their respective elements, to wit, rheostat 17, adjusting means 29 and stepping switch 9. Also coupled to the shaft 3t) is a movable arm 2&5 of the stepping switchZd which, as aforesaid, coacts with the auxiliary winding to compensate for voltage losses which occur due to the movement of movable arm 27 of rheostat 17. Similarly, on the shaft 32 is coupledthe movement of either of the shafts 30 or 31V In addition, in the second position the shafts 30 and 31 are in independent coupling relationship with each other as the movement of either gear of the pair 36:: or 36b will not be transmitted through the gears 36c and 36d to the other gear of the pair.

,Alternatively, the drum 41 may be driven in thefirst position to indicate a ma.-sec.-product as derived with the aid of a chart or table.

To find the combination in which the load period is at a minimum for a given tube voltage either for a maximum permissible tube current ora given percentage thereof, a

suitable safety member means is utilized. For example, the safety member I, FIG. 1, is illustrated therein and in FIG. 2 as comprising a potentiometer 4% connected to a suitable reference source 5%. The'position of movable arm 4d of potentiometer 49 is disposed on the shaft 32, so that any voltage adjustment to tube 10, FIG. 1, causes a signal to be derived at the output of potentiometer 49 movable arm 23 of the resistor 24 which, as aforesaid,

is provided to compensate for voltage losses due to the movements of arm 9' of stepping switch 9 associated with the control transformer 3.

Between the shafts 3t) and 31, a coupling member, illustrated generally by reference numeral 28, comprises a differential gear'system 36. The gears 37 and 39 are keyed, respectively, to shafts 3t and 31 and engage respectively the gears 38 and 4l,'the latter being keyed, respectively, to shafts 38a and 4th. Keyed to the shafts 38a and 453a are the gears 36a and 361), respectively, of the differential gear system 36. The differential gear system 36 is housed in a rotatable drum 41 which has a shaft 41a disposed thereon to support the gears 36c and $64 w ich are meshed with gears 36a and 36b. Associated with the drum 41 is a gear 43 which is adapted to be engaged by the gear 44, the latter being keyed to a shaft which is axially movable along its longitudinal axis by depression. of the'knob 46 attached to the end thereof. The rotatable drum 41 may include, along the periphery thereof, a scale 42 calibrated with reference markings proportional to the product of difierent signal current magnitude and time period combinations. To this end, the shaft 45 may be rotatable and, by depression and a first position in which the shaft 45 is depressed to engage gears 43 and 44 and prevent the rotatable member 41 from rotating about the gears 35a and 35b and allow,

whenever either of the adjusting means associated with I the shafts 3t? and 31 are actuated by movements of their respective knobs 33 and 34, the movements or" these shafts 3d, 31 to be transmitted to the other shaft via gear system 36 andigears 37to 4%. In the second position of the coupling means 28, the gears 44 and 43 are disengaged causing the drum 41 to be in responsive relationship with potential cou which isproportional to the logarithm of the magnitude of the signal voltage applied to tube It A second potentiometer 52 is also coupled to the reference source 50, and the movable arm 51 thereof is actuated by movement of the shaft 31. The signal derived from the output of the potentiometer 52is made proportional to the logarithm of the-maximum permissible kilowatt-secondproduct for tube 153. The signals'derived from potentiometers 49 and 52 are combined in an opposing sense, so that their dif ference represents a signal whose magnitude is proportional to the logarithm of the maximum permissible ma.- sec.-product and is supplied as a reference signal to the input of a comparison circuit '59 to provide a threshold level therefor.

wo serially connected potentiometers 5d and 55, are serially connected to voltage source 53, The movable arm'aio of potentiometer 5 5 is actuated by shaft 30 in response to movements of the circuit adjusting means causing a signal to be derived at the output of potentiometer 54 proportional to the logarithm of the magnitude of the signal current applied to tube 14 f The other potentiometer has its movable arm 57 responsive to movements of shaft 31, via a suitable coupling means 53, illustrated in 'Fig. 2, by Way of example only, as a belt and pulley system, causing a signal to appear at the output thereof proportional to the logarithm of the adjusted load period. The signals derived from the potentiometers S4 and are combined in an aiding sense to'provide a signal proportional to the logarithm of the adjusted ma.-sec.-product for tube 16 which, -in turn, is fed to the comparator 59 where it is compared with the reference signal derived from potentiometers 49 and 52. Comparator 59 provides a signal which is coupled to a signal indicator system as which may be a metercalibrated, for example, to indicate, in percentages, therelationship of the adjusted ma.-sec.-product to the max'unum permissible ma.-sec.-product. 1

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example andnot as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is;

l. A. radiographic apparatus comprising an electron discharge device having a collector electrode and an emitter electrode adapted to produce a beam of'X-rays for radiographic inspection of an object, a first source of (I -ed to said electrodes to provide an open for sai' device, a second source of cutating potenti rent coupled to said emitter electrode to heat said'emitter electrode, timing means to uncouple said first source from said electrodes after a given time period, first adjusting. means coupledjto said first source to adjust the magni- 'tude of said operating potential, second adjusting means coupled to said second source toadjust the magnitude of said heating current,v third adjusting means coupled to said timingrneans to adjust the length of said time period, and coupling means having a first position for coupling said second and third adjusting means in relative responsive relationship with each other to maintain the product of the magnitude of the emitter current and time period constant Whenever either of said second and third adjusting means is adjusted and having a second position for decoupling saidsecond and third adjustingv means from each other whereby either of said second and third adjusting means can be adjusted independently of the other. a

2. A radiographic apparatus according to claim 1, wherein said apparatus further comprises safety means to prevent overloading of said device comprising means for producing a first potential proportional to the logarithm'of the operating voltage applied to said discharge device, means for deriving a second potential proportional to the logarithm of the maximum permissible kilowatt-second product for said discharge devicqmeans for combining said first and second potentials to obtain a first resultant potential proportional to the logarithm of the maximum permissiblecurrent-second product for said discharge device, means for deriving a third potential pro portional to the logarithm of the current in said discharge device, means for producing a fourth potential proportional to the logarithm of a selected exposure time for said discharge device, means for adding said third and fourth potentials to produce a second resultant potential,

means for supplying said first and second resultant poten-' tials to a comparison means to obtain an indicating sigml, and indicating means. responsive to said indicating signal.

3. Apparatus according to claim 1, wherein said coupling means comprises a difierential gear system having a pair of first and second gears, said first and second gears being mounted in responsive coupling relationship with said second and third adjusting means, respectively, a third gear meshed with each .of said first and second gears, said coupling means further comprising control means having a first and second position corresponding to said first and second positions, respectively, of said coupling means, a rotatable member coupled to said differential gear system and adapted to be driven independently by each of said first and second gears in said second position of said coupling means, a shaft disposed on said rotatable member to support said third geaigsaid control means in said first position being arranged to block rotation of said rotata is member thereby to allow said third gear to be driven independently by either gear of said pair of first and second gears thereby to drive the other gear of said pair of gears.

4. Apparatus accroding to claim 3, wherein said rotat able member comprises a drum having a fourth gear dis-. posed thereon, and said control means comprises a rotatable shaft on which is mounted a fifth gear adapted to be meshed with said fourth gear in said first position.

5. Apparatus as described in claim 4 wherein said rotatable drum comprises an indicator scale disposed on the periphery thereof, said scale being calibrated with reference markings proportional to the product of different combinations of current magnitudes and time periods.

6. Control apparatus for a radiographic device com prising an electron discharge device having a collector electrode and an emitter electrode and adapted to produce a beam of electromagnetic energy for radio'graphic in sp-ection of an object, said control apparatus comprising means for energizing said discharge device, said energizing means comprising means for supplying an operating potential to said electrodes and means for: supplying a current to said emitter electrode, timing means for deenergizing said discharge device after a given time period, first adjusting means for varying the magnitude of said operating potential, second adjusting means for varying the magnitude of said emitter current, said timing means comprising third adjusting means for varying said time period, and coupling means having a first position for coupling said second and third adjusting means in rela tive responsive relationship with each other to maintain the product of the magnitude of the emitter current and time period constant Whenever either of said second and third adjusting means is adjusted and having a second positionfor decoupiing said second and third adjusting means from each other whereby either of said second and thirdadjusting means can be adjusted independently of the other.

Eeferences Qited in thefile of this patent UNETED STATES PATENTS 1 2,502,269 Nemet, Mar. 28, 1950 2,835,823 Fransen May 20, 1958 2,870,340 Fransen Jan. 20, 1959 FOREIGN PATENTS 722,350 Germany July 8, 1942 931,305 Germany Aug.4, 1955 

6. CONTROL APPARATUS FOR A RADIOGRAPHIC DEVICE COMPRISING AN ELECTRON DISCHARGE DEVICE HAVING A COLLECTOR ELECTRODE AND AN EMITTER ELECTRODE AND ADAPTED TO PRODUCE A BEAM OF ELECTROMAGNETIC ENERGY FOR RADIOGRAPHIC INSPECTION OF AN OBJECT, SAID CONTROL APPARATUS COMPRISING MEANS FOR ENERGIZING SAID DISCHARGE DEVICE, SAID ENERGIZING MEANS COMPRISING MEANS FOR SUPPLYING AN OPERATING POTENTIAL TO SAID ELECTRODES AND MEANS FOR SUPPLYING A CURRENT TO SAID EMITTER ELECTRODE, TIMING MEANS FOR DEENERGIZING SAID DISCHARGE DEVICE AFTER A GIVEN TIME PERIOD, FIRST ADJUSTING MEANS FOR VARYING THE MAGNITUDE OF SAID OPERATING POTENTIAL, SECOND ADJUSTING MEANS FOR VARYING THE MAGNITUDE OF SAID EMITTER CURRENT, SAID TIMING MEANS COMPRISING THIRD ADJUSTING MEANS FOR VARYING SAID TIME PERIOD, AND COUPLING MEANS HAVING A FIRST POSITION FOR COUPLING SAID SECOND AND THIRD ADJUSTING MEANS IN RELATIVE RESPONSIVE RELATIONSHIP WITH EACH OTHER TO MAINTAIN THE PRODUCT OF THE MAGNITUDE OF THE EMITTER CURRENT AND TIME PERIOD CONSTANT WHENEVER EITHER OF SAID SECOND AND THIRD ADJUSTING MEANS IS ADJUSTED AND HAVING A SECOND POSITION FOR DECOUPLING SAID SECOND AND THIRD ADJUSTING MEANS FROM EACH OTHER WHEREBY EITHER OF SAID SECOND AND THIRD ADJUSTING MEANS CAN BE ADJUSTED INDEPENDENTLY OF THE OTHER. 